JPH0749621Y2 - Optical head structure of optical information recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention focuses laser light from a laser light source on an information surface of an optical disc through an optical system, records or erases information on the information surface, and The present invention relates to an optical head structure of an optical information recording / reproducing apparatus that detects reflected laser light from a surface and reads recorded information.

[Prior Art] Conventionally, there is an optical head configured as shown in FIG. 4 as an optical head of an information recording / reproducing apparatus for an optical disc.

This is a beam splitter 4 as an optical path splitting element in which a laser beam emitted from a semiconductor laser 1 is collimated by a collimator lens 2 and then a shaping prism 3 for shaping the beam cross section into a circular shape is integrally formed. The optical disc 10 is made to pass through and reflected by the rising mirror 5.
In addition to being guided in the direction, the objective lens 6 converges and irradiates the information signal recording surface on the optical disc 10.

When recording information, information is recorded or read (reproduced) by physically or chemically changing the laser beam energy on the information signal recording surface.
At this time, the laser beam reflected on the information signal recording surface and tracing the outward path in reverse is the half mirror surface of the beam splitter 4.
In 4a, the optical path is bent at a right angle to the forward path and the phase plate (1 / 2λ
After passing through the plate 9 to a photodetector (not shown), a reproduction signal is obtained by being detected by the photodetector. In addition to the reproduction signal, a tracking error signal and a focusing error signal can be obtained from the photodetector, and the operation control of the optical head is performed based on these error signals. It is a thing.

With such a rewritable optical head configuration, the transmittance of 60 to
Since 80% of beam splitter 4 is used, semiconductor laser 1
The laser beam emitted from the beam splitter 4
When passing through, part (20-40%) is a half mirror surface
It is reflected by 4a and is emitted to the outside of the beam splitter 4. The laser beam (reflected light beam) emitted to the outside of the beam splitter 4 does not contribute to recording or reproduction at all, but this reflected light beam is condensed by the condenser lens 7 on the monitor photodetector 8 and The drive of the semiconductor laser 1 is feedback-controlled based on the reflected light flux detection output of the photodetector 8 to obtain a stable laser beam output.

That is, since the light quantity of the reflected light flux emitted to the outside of the beam splitter 4 is proportional to the light quantity of the laser beam emitted from the semiconductor laser 1, the light quantity of this reflected light flux is detected by the monitor photodetector 8 and the laser light is detected. The beam output can be grasped so that the semiconductor laser 1 can be driven and controlled.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, a condenser lens for monitoring is arranged near the beam splitter as shown in FIG. 5 which is a view taken along the line IV-IV in FIG. At the same time, the monitor photodetector must be placed at the focal position, and the monitor components must be configured so as not to interfere with the actuator of the objective lens and the like, resulting in an increase in the size of the entire optical head. There was a problem.

[Purpose of the Invention] In view of the above situation, the present invention can increase the use space in the vicinity of the beam splitter by arranging monitor components such as a condenser lens and a monitor photodetector three-dimensionally. It is another object of the present invention to provide an optical head structure of an optical information recording / reproducing device which can make the entire optical head compact.

[Means for Solving the Problem] Therefore, the optical head structure of the optical information recording / reproducing apparatus according to the present invention is emitted from the laser light source, is bent by the optical path dividing element, and is emitted to the outside from the optical path dividing element. The laser light is bent by the total reflection prism and guided to the monitor light detector, and the output of the laser light source is controlled by the laser light detection output by the monitor light detector, and the incident surface of the total reflection prism is changed to the total reflection prism. It is configured by inclining at a predetermined angle from the right angle to the incident optical axis.

[Embodiment of the Invention] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of an optical head structure of an optical information recording / reproducing apparatus according to the present invention.

The illustrated optical head structure consists of a semiconductor laser 1 and a collimator lens.
2, and shaping prism 3 that shapes the beam cross section into a circle
A beam splitter 4, which is an optical path splitting element integrally formed with, is arranged in series.

A raising mirror 5 is arranged on the side of the beam splitter 4 through which the laser beam from the semiconductor laser 1 is transmitted and emitted, and a part of the laser beam 20 from the semiconductor laser 1 is reflected by the half mirror surface 4a. The total reflection prism 11 as a bending member and the condenser lens 12 in front of the optical path reflected and bent by the total reflection prism 11 on the side where the light is emitted.
Also, a monitoring photodiode 13 as a photodetector is arranged. A phase plate (1 / 2λ plate) 9 is provided on the side surface of the beam splitter 4 facing the side where the total reflection prism 11 is arranged.
Are arranged.

The total reflection prism 11 is a so-called right-angled prism, and is arranged so as to bend the reflected laser beam 22 emitted from the beam splitter 4 downward at a substantially right angle. The condenser lens 12 and the monitor photodiode are arranged in the prism. Reference numeral 13 is arranged substantially vertically along the bent light flux.

The incident surface 11a of the total reflection prism 11 is, as shown in FIG.
The reflection laser beam 22 is arranged not at right angles to the optical axis but at a predetermined angle (θ = 1 to 2 °).

The output of the monitor photodiode 13 is input to a controller (not shown) of the semiconductor laser 1, and the output of the semiconductor laser 1 is feedback-controlled based on the output of the monitor photodiode 13. ing.

Thus, in the optical head configured as described above, the laser beam 20 emitted from the semiconductor laser 1 is collimated by the collimator lens 2 and enters the beam splitter 4 from the shaping prism 3 side.

Here, the laser beam is shaped by the shaping prism 3 into a circular beam cross-sectional shape, and is transmitted or reflected by the half mirror surface 4a at a predetermined branching ratio as shown in FIG. (For example, the transmitted laser beam: 60 to 80%, the reflected laser beam: 40 to 20%) The transmitted laser beam 21 transmitted through the half mirror surface 4a is emitted from the beam splitter 4 and is reflected by the rising prism 5 as well. It is condensed by an objective lens (not shown) and converged and irradiated onto the information recording surface of the optical disc (not shown).

The reflected laser beam 22 reflected by the half mirror surface 4a and emitted to the outside of the beam splitter 4 is reflected by the total reflection prism 11 to be bent in the optical path downward, converged by the condenser lens 12 and converged on the monitor photodiode 13. Incident.

The amount of light incident on the monitor photodiode 13 is completely proportional to the amount of light emitted from the semiconductor laser 1. Therefore, the laser beam output can be accurately grasped from the detection output of the reflected laser beam 22 by the monitoring photodiode 13, and a constant laser output can be obtained by feedback controlling the semiconductor laser 1 using this output signal. be able to. Further, since the return light from the optical disk does not enter the monitor photodiode 13, stable control without disturbance can be performed.

It should be noted that the transmitted laser beam 21 which is transmitted through the beam splitter 4 and converged and radiated to the information recording surface of the optical disc causes a physical or chemical change on the information signal recording surface by the laser beam energy when recording information. When recording (reproducing) information while recording information by using the laser beam 21 'reflected on the information signal recording surface, the laser beam 21' follows the reverse path, and the half mirror 4a of the beam splitter 4 changes the optical path to the forward path. It is bent at a right angle, passes through the phase plate 9 and reaches a photodiode (not shown) for detecting a reproduction signal, and the reproduction signal is obtained by the photodiode for detecting the reproduction signal.

With the above-mentioned configuration, as shown in FIG. 3 which is a view taken along the line III-III in FIG. 1, the arrangement parts in the vicinity of the periphery of the beam splitter 4 become easy and the space for use shown by the diagonal lines in the drawing increases, Further, the planar shape of the entire optical head can be made compact.

With the above configuration, the reflected laser beam 22 is reflected by the incident surface 11a of the total reflection prism 22, and the half mirror 4
It is possible to prevent the generation of noise due to an erroneous signal being transmitted through a photodiode for reproducing signal detection after passing through a, or being reflected by the half mirror 4a and returning to the semiconductor laser 1.

[Advantages of the Invention] According to the optical head structure of the optical information recording / reproducing apparatus according to the present invention, the degree of freedom in designing the arrangement of components is increased, and the optical head is conventionally occupied by the condenser lens and the monitor photodetector. It is possible to effectively use the space around the beam splitter. Further, the planar shape of the entire optical head can be made compact.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic structure of an embodiment of an optical head structure of an optical information recording / reproducing apparatus according to the present invention, FIG. 2 is its plan view, and FIG. 3 is III-III of FIG. FIG. 4 is a perspective view of a conventional example, and FIG. 5 is a IV-IV arrow view thereof. 1 ... Semiconductor laser (laser light source) 4 ... Beam splitter (optical path splitting element) 11 ... Total reflection prism (optical path bending member) 11a ... Incident surface (incident surface of total reflection prism) 13 ... Monitor photodiode (Monitor light detector) 20 ... Laser beam (laser light from laser light source) 22 ... Reflected laser beam (laser light refracted by the optical path splitting element and emitted to the outside from the optical path splitting element)

Claims (1)

[Scope of utility model registration request] 1. An optical disc information surface is irradiated with laser light from a laser light source through an optical path dividing element to record information, and reflected laser light from the optical disc information surface is bent by the optical path dividing element to generate light. An optical head structure of an optical information recording / reproducing device that guides a detector, wherein laser light emitted from a laser light source, bent by the optical path splitting element, and emitted to the outside from the optical path splitting element is bent by a total reflection prism. Guide to the monitor photodetector, while controlling the output of the laser light source by the laser light detection output by the monitor photodetector, the incident surface of the total reflection prism, relative to the incident optical axis to the total reflection prism The optical head structure of the optical information recording / reproducing apparatus is characterized in that the optical head is tilted at a predetermined angle from a right angle.